The present invention relates to a circuit device for supplying a direct voltage and at least one high frequency signal to a diode disposed in a waveguide, the diode being in contact with the inner conductor of a coaxial cable supplying the DC voltage.
Such a device is disclosed in Federal Republic of Germany Application No. 31 38 173 A1. In the parametric amplifier on which this document is based, a coaxial line supplies a diode with a high frequency signal in addition to a DC voltage. The simultaneous coupling of both signals into the coaxial line is relatively complicated. In addition, the spring required to maintain the inner conductor of the coaxial line in contact with the diode can not be prevented from having adverse influence on the high frequency signal, primarily if it is a very high frequency signal (&gt;10 GHz). The coaxial line also has the drawback that it does not offer variable tuning of the diode impedance to the high frequency signal. Variable tuning of the coaxial line would be very difficult, if not impossible, to realize.